An investigation on the Fluctuation and variability of ambient noise in shallow waters of south west Bay of Bengal

Abstract

Variability of ambient noise in shallow south west Bay of Bengal is investigated in the band 0.5 - 5.0 kHz using time series measurements during Sept-Nov 2010. Data is segregated into southwest, transition and northeast monsoon on the basis of seasons. Variability of Noise Level (NL) at the site is mainly influenced by wind, shipping and biological activity along with precipitation (during transition and northeast monsoon). NL increases and generates broadband peaks in the band 2-4 kHz due to heavy precipitation. In general, average NL increases as the season progresses from southwest to northeast through transition period. But the variability in NL, reported in terms of Standard Deviation (SD) <img src='http://www.niscair.res.in/jinfo/sigma1.gif' border=0>, is high during transition (due to passage of tropical cyclones), followed by southwest and northeast period. SD decreases with increase in Beaufort (Bft), with ó of <2.50 dB for frequency >2.0 kHz for 5 Bft. The observed NL is compared with standard wind generated noise spectra.